1. Field of the Invention
This invention pertains to electrical contacts. In particular, this invention pertains to electrical contacts between and for interconnecting spaced printed circuit boards (PCBs) and/or off-board components. The electrical contact includes a deformable segment adapted to alleviate stress on the connections with slight changes in the spacing between the PCBs.
2. Description of the Related Art
Numerous electrical contact designs have been developed for connecting a printed circuit board (hereinafter “PCB”) with off-board component and/or other PCBs. Representative contact designs include pins, posts, lugs, and tabs.
Surface mounting technology (“SMT”) is a widely used method of securing electrical contacts to PCBs. This method includes providing an electrical contact to a “pick-and-place” machine, which picks up the electrical contact and places it at a predetermined position on a conductive pad or land on the surface of a PCB. The contact is then usually soldered to the PCB.
Once the base of the contact is secured to a PCB, the tip of the contact may be secured to a second PCB or an off-board component using a variety of techniques, including soldering, friction fitting, and clamping. For example, the tip of the contact can be fitted through an aperture or hole within a second PCB, using a through-the-hole (TTH) approach, and held within the aperture by friction and/or subsequent soldering.
In general, a contact is attached to a PCB using a rigid or inflexible bond, such as soldering. Unfortunately, these rigid, relatively small bonds are not able to resist much mechanical stress. Thus, relative movement of connected PCBs, for example, due to thermal expansion, often results in broken bonds and/or contacts.
To alleviate mechanical stress created by relative movement of the interconnected parts, electrical contacts that are deformable, compliant, and/or flexible are used as connections between PCBs and/or off-board components. For example, compliant electrical contacts are described in U.S. Pat. Nos. 4,642,889, 4,751,119, 5,317,479, 5,446,161, and 6,184,587. However, these previously described compliant electrical contacts do not have at least one deformable section that is symmetrical or otherwise balanced about the centerline thereof and, thus, are prone to uneven deformation and excessive lateral flexibility. In the case of pin-shaped contacts, the applicants are unaware of any prior example having at least one symmetrical or otherwise balanced compliant section.
Electrical contacts that are internally re-enforced by solder have also been developed, as described in U.S. Pat. No. 5,816,868 (assigned to Zierick Manufacturing Corp.). The solder wicks or flows from the conductive land on the PCB into a channel within the electrical contact. However, if too much solder is wicked away from the conductive land, the bond between the conductive land and the electrical contact is weakened. Excessive capillary flow of solder is especially troublesome for pin contacts, which often have small bases and long pin sections that wick a relatively large amount of solder from the conductive land.